The present invention relates generally to annealing, and specifically to an annealing sheave comprising a renewable, annealer band adapted to continuously physically and magnetically center the strand being annealed to increase band and sheave longevity, and adapted to prevent arcing.
Annealing is the well known art of heat treating metals and is used to strengthen strands of metal such as wire or cable. The early art introduced batches of product into an oven for annealing but the process was slow and expensive. Continuous processes such as those shown in U.S. Pat. Nos. 1,993,400 and 2,726,971 were developed to continuously anneal wire by passing it along a series of rollers which apply electric current to the advancing wire to heat it as desired. A similar process for annealing cable is taught by U.S. Pat. No. 3,746,582. Originally, the rollers comprised sheaves having a groove in which the advancing strand traveled. It was found that the strand quickly wore out the sheaves because of continuous abrasion so replaceable sheave inserts such as the one shown in West German Pat. No. DT 25 20 161 were developed.
The insert is normally an endless flat strip forming the base of the groove while the sheave portions form the side walls. Although the replacable insert decreases wear on the sheaves somewhat, sheave wear has remained unacceptably high until the present invention because the strand had no propensity to remain in contact only with the insert. Instead, the strand normally moved to one side and began to wear the sheave wall. In addition to having no tendency to remain centered on the insert surface, the strand even if not a magnetic material is often actually attracted to one side by the eddy current fields which are influenced by the mass of the annealer structure.
In addition to wearing out the inner flange surfaces of the sheaves, the strand quickly wears out the insert which is designed to receive the bulk of the wear. Another problem is arcing which causes burn pits to the strand and to the sheaves. The present invention solves the sheave wear and arcing problems by providing an annealing sheave comprising annealer band which continuously centers the strand, extends the life of the band by having a renewable surface, and eliminates detrimental arcing by having certain insulated surfaces.